Interpretive Summary: Unfortunately, the application of dextranase (an enzyme) to break down long chains of unwanted dextran in U.S. sugarcane factories is still not optimized because of misinformation about which enzyme to use, and how and where to add the enzyme. Factory trials were conducted to provide more optimum conditions. The factory had relatively low levels of dextran, that made addition of dextranases more problematic because of lower contact between the dextranase and dextran. Juice from mud tanks contains dextran which must be recirculated back to maximise the use of dextranase. Dextranase applications did not always alleviate all processing problems in the factory because other unwanted products still exist which detrimentally affect processing. Therefore, dextranase application can only be seen as a secondary tool.

Technical Abstract:
This paper continues a report on 2004 Louisiana factory trials of dextranase optimization. As previous laboratory studies had shown dextranase applications to syrup were uneconomical, only juice applications were studied. Part II of this study reports optimization trials at a factory that applied dextranase to a 17 min retention time incubation tank. Working solutions of “concentrated” dextranase in water were required to improve contact between the enzyme and substrate (dextranase/dextran) and are more cost-effective than adding “non-concentrated” dextranases. The factory had relatively low levels of antibody dextran (<300 ppm/oBrix) compared to those reported in the factory in Part I of this study (Eggleston et al, 2006). The addition of dextranases was more problematic because of lower contact between dextranase and dextran. Addition of 5-fold working solutions (5 ppm; normalized to the original enzyme activity) of “concentrated” dextranase (50,500 DU/ml) broke down ~43 % antibody dextran. Filtrate juice from the mud tank was found to contain dextran often at higher levels than in juice where dextranase was applied. Factories should recirculate the filtrate back to the juice before or where they add dextranase, to maximize the use of the enzyme. Differences in dextran breakdown were compared using both antibody and Haze methods: the Haze method underestimated breakdown compared to the antibody method. As dextranase application did not always alleviate all processing problems in factory boiling stations, because lower molecular weight dextrans and other major Leuconostoc mesenteroides deterioration products such as mannitol still exist which detrimentally affect processing, it can only be regarded as a secondary tool. It does not replace the primary tool of prevention of dextran forming by good cane management in the field, factory yard, and factory mills.